Process of preventing corrosion



3,018,246 PROCESS OF PREVENTENG CORROSIGN William B. Hughes and Verner L. Stromberg, St. Louis, Mo., assignors to Petrolite Corporation, Wilmington, DeL, a corporation of Delaware No Drawing. Original application Feb. 3, 1958, Ser. No. 712,662, now Patent No. 2,987,515, dated June 6, 1951. Divided and this application Dec. 4, 1959, Ser. No. 857,263

22 Claims. (Cl. 252-855) This is a division of our application S.N. 712,662, filed February 3, 1958, now US. Patent No. 2,987,515.

This invention relates to urethanes of hydroxy-aliphatic cyclic amidines and more particularly to the diurethanes of imidazolines and tetrahydropyrimides. This invention also relates to a process of preparing these compounds which comprises reacting a hydroxyaliphatic cyclic amidine, for example, a hydroxyaliphatic imidazoline or tetrahydropyrimidine with an organic isocyanate, but preferably an organic diisocyanate. This invention also relates to a process of using these urethanes as corrosive inhibitors in preventing the corrosion of metals, most particularly iron, steel and ferrous alloys.

Heretofore, a Wide variety of cyclic amidine compounds have been employed to inhibit the corrosion of oil well equipment. Although we had expected that hydroxy-aliphatic cyclic amidines would also be very effective in inhibiting oil field corrosion, we found that these compounds had very poor corrosion inhibiting properties.

However, we have now unexpectedly discovered that the derivatives of these hydroxyaliphatic cyclic amidines, particularly the diurethane derivatives thereof, are very efiective corrosion inhibitors, in many cases from 10-15 or more times as effective as the corresponding hydroxyaliphatic cyclic amidine.

The corrosion inhibitors disclosed herein are particularly useful in preventing the corrosion of oil equipment, for example, in producing wells, pipe lines, refineries, tank storage, etc., which are in contact with corrosive oil-containing medium, for example, in oil wells producing corrosive oil or oil-brine mixtures in refineries, and the like. These compositions possess properties which impart to metals resistance to attack by a wide variety of corrosive agents, among which may be mentioned brines, organic and inorganic acids, CO H 0, etc. and combinations thereof.

More specifically, the above-described cyclic amidine compounds may be described by the formulae:

(The dotted lines indicate the undetermined structure, probably polymeric.)

are the residual radicals derived from the carboxylic acids where R comprises, for example, a saturated or unsaturated aliphatic radical, a cycloaliphatic radical, an aryl radical, an aralkyl radical, an alkaryl radical, an alkoxyalkyl radical, an aryloxyalkyl radical, and the like, and A is an alkylene group, for example, ethylene and propylene radicals, or substituted derivatives thereof, such as and R is the urethane product of the reaction of a hydroxy-containing alkylene, polyoxyalkylene, etc., groups with an isocyanate.

More specifically, the corrosion inhibiting aspect of this invention relates to a method for inhibiting corrosion of ferrous metals by hydrocarbon fluids containing water and corrosive materials such as H S, CO inorganic acids, organic acids, etc, combinations of these materials with each other, combinations of each of said corrosive materials with oxygen, and combinations of said materials with each other and oxygen, which comprises treating ferrous metals such as by adding to said fluids at least 5 parts per million of the above urethane compounds, said compounds being sufiiciently soluble in the hydrocarbon fluid to inhibit corrosion.

THE HYDROXY ALIPHATIC CYCLIC AMIDINE The expression cyclic amidines is employed in its usual sense to indicate ring compounds in which there are present either 5 or 6 members, and having 2 nitrogen atoms separated by a single carbon atom supplemented by either two additional carbon atoms or three addi- 3 tional carbon atoms completing the ring. All the carbon atoms may be substituted. In the present instance the nitrogen atom of the ring involving two monovalent linkages (the 1-position) is substituted with an hydroxy aliphatic group, i.e., (RO),,H groups where R is alkylene and n is a whole number, for example, 1-5 or higher.

These cyclic amidines are further characterized as be ing substituted imidazolines and tetrahydropyrimidines in which the two-position carbon of the ring is generally bonded to a hydrocarbon radical or comparable radical derived from an acid, such as a low molal fatty acid, a high molal fatty acid, or comparable acids, polycarboxy acids, and the like.

For details of the preparation of imidazoline substituted in the 2-position from amines, see the following U.S. patents, U.S. No. 1,999,989, dated April 30, 1935, Max Bockmuhl et al.; U.S. No. 2,155,877, dated April 25, 1939, Edmund Waldmann et al. Also see Chem. Rev. 32,47 (43), and Chem. Rev. 54,593 (54).

Equally suitable for use in preparing compounds use- 111 in our invention and for the preparation of tetrahydropyrimidines substituted in the 2-position are the corresponding polyamines containing at least one primary amino group and one secondary amino group, or another primary amino group separated from the first primary amino group by three carbon atoms instead of being separated by only 2 carbons as with imidazolines. This reaction as in the case of the imidazoline is generally carried out by heating the reactants to a temperature at which 2 moles of water are evolved and ring closure is effected. For details of the preparation of tetrahydropyrimidines, see German Patent No. 700,371, dated December 18, 1940 to Edmund Waldmann and August Chwala; German Patent No. 701,322, dated January 14, 1941, to Karl Kiescher, Ernst Urech and Willi K-larer and U.S. Patent No. 2,194,419, dated March 19, 1940 to August Chwala. Substituted imidazolines and tetrahydropyrimidine are obtained from a variety of acids beginning with the one-carbon acid (formic) through and including higher fatty acids or the equivalent having as many as 30 carbon atoms, for example from 8-22 carbons. Modified fatty acids also can be employed as, for example, phenyl stearic acid or the like. Cyclic acids may be employed, including naphthenic acids. A variety of other acids including benzoic acid, substituted benzoic acid, salicyclic acid, and the like, have been employed to furnish the residue from the acid RCOOH in which the C of the residue ll RC- is part of the ring. The fatty acids employed, for example, may be saturated or unsaturated. They may be hydroxy-lated or nonhydroxylated. Branched long chain fatty acids may be employed. See J. Am. Chem. Soc. 74,2523 (1952). This applies also to the lower molecular weight of acids as well. I

Among sources of such acids may be mentioned straight chain and branched chain, saturated and unsaturated, aliphatic, cycloaliphatic, aromatic, hydro-aromatic, aralkyl acids, etc.

Examples of saturated aliphatic monocarboxylic acids comprise: acetic, propionic, butyric, Valerie, caproic, heptanoic, caprylic, nonauoic, capric, undecanoic, lauric, tridecanoic, myriatic, pentadecanoic, palrnitic, heptadecanoic, stearic, nonadecanoic, eicosanoic, heneicosanoic, docosanoic, tricosanoic, tetracosanoic, pentacosanoic, cerotic, heptacosanoic, montanic, nonacosanoic, melisaic and the like.

Examples of ethylenic unsaturated aliphatic acids comprise: acrylic, methacrylic, crotonic, anglic, teglic, the pentenoic acids, the hexenoic acids, for example, hydrosorbic acid, the heptauoic acids, the octenoic acids, the nonenoic acids, the decenoic acids, for example, obtusilic acid, the undecenoic acids, the dodecenoic acids, for example, lauroleic, linderic, etc., the tridecenoic acids, the tertadecenoic acids, for example, myristoleic acid, the pentadecenoic acids, the hexadecenoic acids, for example, palrnitoleic acid, the heptadecenoic acids, the octodecenoic acids, for example, petrosilenic acid, oleic acid, ola-idic acid, the nonadecenoic acids, for example, the eicosenoic acids, the docosenoic acids, for example, erucic acid, brassidic acid, cetoleic acid, the tetracosenic acids, and the like.

Examples of dienoic acids comprise the pentadienoic acids, the hexadienoic acids, for example, sorbic acid, the octadienoic acids, for example, linoleic, and the like.

Examples of the trienoic acids comprise the octadecatrienoic acids, for example, linolenic acid, eleostearic acid, pseudoeleostearic acid, and the like.

Carboxylic acids containing functional groups such as hydroxy groups can be employed. Hydroxy acids, particularly the alpha hydroxy acids comprise glycolic acid, lactic acid, the hydroxyvaleric acids, the hydroxy caproic acids, the hydroxyheptanoic acids, the hydroxy caprylic acids, the hydroxynonanoic acids, the hydroxycapric acids, the hydroxydecanoic acids, the hydroxy lauric acids, the hydroxy tridecanoic acids, the hydroxymyristic acids, the hydroxypentadecanoic acids, the hydroxypalmitic acids, the hydroxyhexadecanoic acids, the hydroxy heptadecanoic acids, the hydroxy stearic acids, the hydroxyoctadecenoic acids, for example ricinoleic acid, ricinelaidic acid, hydroxyoctadecynoic acids, for example, ricinstearolic acid, the hydroxyeicosanoic acids, for example, hydroxyarchidic acid, the hydroxydocosanoic acids, for example, hydroxybehenic acid, and the like.

Examples of acetylated hydroxyacids comprise ricinoleyl lactic acid, acetyl ricinoleic acid, chloroacetyl ricinoleic acid, and the like.

Examples of the cyclic aliphatic carboxylic acids comprise those found in petroleum called naphthenic acids, hydrocarbic and chaumoogric acids, cyclopentane carboxylic acids, cyclohexanecarboxylic acid, campholic acid, fencholic acids, and the like.

Examples of aromatic monocarboxylic acids comprise benzoic acid, substituted benzoic acids, for example, the toluic acids, the xyleneoic acids, alkoxy benzoic acid, phenyl benzoic acid, naphthalene carboxylic acid, and the like.

Mixed higher fatty acids derived from animal or vegetable sources, for example, lard, cocoanut oil, rapeseed oil, sesame oil, palm kernel oil, palm oil, olive oil, corn oil, cottonseed oil, sardine oil, tallow, soyabean oil, peanut oil, castor oil, seal oils, Whale oil, shark oil, and other fish oils, teaseed oil, partially or completely hydrogenated animal and vegetable oils are advantageously employed. Fatty and similar acids include those derived from various waxes, such as beeswax, spermaceti, montan wax, Japan wax, coccerin and carnauba wax. Such acids include carnaubic acid, cerotic acid, lacceric acid, montanic acid, psyllastearic acid. etc. One may also employ higher molecular weight carboxylic acids derived by oxidation and other methods, such as from parafiin wax, petroleum and similar hydrocarbons; resinic and hydro-aromatic acids, such as hexahydrobenzoic acid, hydrogenated naphthoic, hydrogenated carboxy diphenyl, naphthenic, and ahietic acid; aralkyl and aromatic acids, such as Twitchell fafty acids, naphthoic acid, carboxydiphenyl pyridine carboxylic acid, blown oils, blown oil fatty acids and the like.

Other suitable acids include phenylstearic acid, benzoylnonylic acid, cetyloxybutyric acid, cetyloxyacetic acid, chlorstearic acid, etc.

Examples of the polycarboxylic acids comprise those of the aliphatic series, for example, oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, nonanedicarboxylic :acid, decanedicarboxylic acids, undecanedicarboxylic acids, and the like.

Examples of unsaturated aliphatic polycarboxylic acids comprise fumaric, maleic, mesoconic, citraconic, glutonic, itaconic, muconic, acenitic acids, and the like.

Examples of aromatic polycarboxylic acids comprise phthalic, isophthalic acids, terephthalic acids, substituted derivatives thereof (e.g. alkyl, chloro, alkoxy, etc. derivatives), b iphenyldicarboxylic acid, diphenylether dicarboxylic acids, diphenylsulfone dicarboxylic acids and the like.

Higher aromatic polycarboxylic acids containing more than two carboxylic groups comprise homimellitic, trimellitic, 'trimesic, mellophanic, prehnitic, pyromellitic acids, mellitic acid, and the like.

Other polycanboxylic acids comprise the dimeric, trimeric and poly acids, for example, Emery Industries polymeric acids (such as those described in US. Patent 2,763,612) and the like. Other polycarboxylic acids comprise those containing ether groups, for example diglycollic acid. Mixtures of the above acids can be advantageously employed.

In addition, acid precursors such as esters, acid chloride, glycerides, etc. can be employed in place of the free acid.

Where the acid contains functional groups such as hydroxy groups, this should be taken into consideration in subsequent reaction with the isocyanate in calculating the storchronity of the reaction.

Hydroxy substituted imidazolines and tetrahydropyrimidines can be obtained the manner described above from a wide variety of polyamines containing hydroxy groups. Thus, where one starts with a polyamine, for example, a diamine of the following formula where R has 2 or 3 carbon chains in the main chain, one obtains the hydroxyalkylene compounds useful in this invention. In addition, one can start with ethylene diamine or with 1,2-propylene diamine, 1,3-propylene-diamine or other polyamines and then react the cyclic amidine so obtained with alkylene oxides so as to produce a terminal hydroxy group since the nitrogen bonded hydrogen on the 1-position on the ring reacts with alkylene oxides. In addition the hydroxyalkylene group can be oxyalkylated.

Alkylene oxides comprise those of the general formula,

where R is hydrogen or an alkyl group. Among the alkylene oxides that may be employed are ethylene, propylene, butylene, octylene, etc. oxides, etc. Other oxyalkylation agents such as glycide, epichloro hydrine, etc. can also be employed.

Thus hydroxy compounds within the scope of this invention which react with isocyanates comprise compounds of the formulae:

where RC- is the residue derived from the carboxylic acid, where R is a hydrocarbon radical having, for example, up to about 30 carbon atoms, hydrocarbons in which the carbon atom chain is interrupted by oxygen, etc., n is 2 or 3; and B is a hydrogen or a hydrocarbon radical, for example, a alkyl radical; and D is a hydroxy aliphatic radical, for example ROH or -('RO) OH, wherein x is a whole number, for example, 1-10, but preferably 1-5, and CB is, for example, a divalent radical of the formula: CH -CH -CH --CH CH In general, the hydroxyalkyl cyclic amidines are prepared by reacting a polyamine containing a terminal alkanol group with a carboxylic acid at temperatures of from 175 C. employing an azeotroping agent such 'as xylene to remove water. A reaction time of 3-4 hours is employed. Completion of reaction is judged by the separation of 2 moles of H 0 for each carboxylic acid group. The products are in general dark viscous oils.

Since the praparation of cyclic amidines is so well known (see above cited patents) it is not believed that any examples are necessary to illustrate such a well known procedure. However, for purposes of illustration the following are included.

EXAMPLE 100 A solution of 1 mole of hydroxyethyl ethylene diamine,

HO CHiCHzNCHzCHtNHa and 1 mole of oleic acid in 300 grams of xylene are charged to a flask and brought to reflux, the mixture being heated under a Dean-Stark water trap, condenser in order to distill off the water-xylene azeotrope mixture, to separate the water and to continuously return xylene to the reaction mixture. Reflux is continued at a temperature of -170 C. for about 3 /2 hours until about 2 moles of water is removed. The product is GII CH;|

N N-CHzCHzOH F CnHss EXAMPLE 9b The above example is repeated except that hydroxyethyl propylene diamine 1-3,

t HO OIIflOHiN-CH2CH2CH2NH2 is employed in place of hydroxyethylethylene diamine and stearic acid is employed in place of oleic acid. The product produced is )3 CHa-CH N N-CHz-CHaOH CnHss EXAMPLE 40 Example 10a is repeated with the same amine HO OHzCHzIYICHgCHzNH: H

(2 moles), except that a polycarboxylic acid, sebacic acid (1 mole) is employed. Instead of two moles of water being removed, as in the prior example, about 4 moles of water are removed. The product is EXAMPLE 20d Example 40 is repeated except that a difierent amine,

HOCH:|CH21I TCHzCH:CHaNH2 (2 moles) and a difierent polycarboxylic acid, terephthalic acid (1 mole), are employed. As in the prior example,

4 moles of water are removed. The product is CH2 /C]{: (3H1 10H: (EH2 (3H2 HOCH2CH:N N N N-CHzCHzOH In general, to form the polyoxyalkylated hydroxy cyclic amidines, the hydroxyalkylcyclic amidine is first prepared in the manner shown above and then reacted with alkylene oxides by the conventional manner of oxyalkylation to the desired degree of oxyalkylation using a jacketed stainless steel autoclave in the manner described in US. Patent 2,792,369. The following examples are illustrative:

EXAMPLE 11a One mole of (50% solution in xylene) is reacted with 1 mole of ethylene oxide at a temperature of 125 130" C. and a pressure of -15 p.s.i. The time regulator is set to add ethylene oxide over /2 hour followed by additional stirring for another /2 hour to insure complete reaction. Ethylene oxide is readily taken up by the reactants. The product is The above example is repeated using a propylene oxide and uHn under similar conditions. The product is CH2CH2 CH3 CH3 C nHz:

us in preparing other hydroxycyclic amidines of these types are listed in the following t-ables: 4

TABLE I ROOOH source ofRC R Laurie CH2 CH2 0 H Hexanoic- CHQOHZOH CHzCHzOH CHnCHaOH CHzCHzOH CHzCHuOH CHzCHzOH CH2CH2OH CHzCHzOH CHZOHQOCHRCHQOH CH (11H: HaCHgOCHgCHnOH Laurie CHgCHaO CH3CH2OH Palmitic- CHgCHzO CHzCHzOH Cerotic CHaCHaO CHzCHaOH p-tert-Buty1benzo1e.. CH CHgO CHzCHzOH Benzoic CH2C'H30 CHaCHzOH T011110 CHQOHQO CH2CH2OH CHzCHzOCHzCHaOH CHzCHzOCHzCHzOH OHCH2O CHgCHaO CHaCHzOH CHzCHzO CHzCHaO CHICHaOH CHflC/HQO CHzCHzO CHICHEQE CHgCHzO C2H1OB1O CHgCHgOH CHaCHzO CzHnCHzO CH CH:OH CHzCHzO CzHzCHzO CHiOHZOH CHzCHzO CgHzCHzO CHzCHzOH CHzCHzO CzHzCHzO CHICHzOH CHzCHzO CzHaCHzO CHzCHaOH CHzCHzO CzHnCHgO CHgCHgOH Oreosotiuic. Naphthenic CHzCHzOH CHzCHaOH flCHZOH (CH3)OH:CH1OH 2CH2OH :CHIOH CHnCHzOCHqCHzOH CHaCH OH CHzCHzOH (CH3) CHzGHgOH CHzCHgOH CHzCHzOH CHzCHzOH CHgCHgOCHzOHgOH CHzCHzOH CHHGHZOH CHzCHzOH CHnCHzOH CHIOHzOH CH2CH2OH CHZCHQOH CHgCHzOH CHQCHQOH CHzCHzOH Undecylenic Lin0leic Butyric Methyloctadecanoic.

TABLE III Ex HOOCRCOOH R No source of ORC CH2CH2OH CHzCH2OH CHzCHzOH GH2CH2OH 5c--. Nonodecane dicar- CH2CH2OH boxylic. 60"- Diglycolic CH2CH2OH 7c. Ethylene bis (glycolic) CH2OH2OH 8c--- Methylene dibenzoic.. CH2CH2OH 9c--- Stearyl malonic-. CHzCHzOH 100-. Phthalic CHzCHzOH 110.. Succinic CHzOHzOCHzCHzOH 120.- Glutaric CHZCH2OOH2CHQOH 130 P11116110 CHzCHgOCHzCHgOH 140-. Azelaic" CH2CH2OCH2OH2OH 150.. Eicosane OH2OH2OCH2OH2OH 160.- Dilinoleic. CHzCHgOOHzCHgOH 170.- Isophthalic CHzCHzOCHzCHzOH 180-- Diglycolie. CH2CH2OCH2CH2OH 190.. Lauryl malonic--.- CHeCHzOCHzCH-zOH 200-. Methylene dibenz0ic.. CH2CH2OCH2CH2OH 210.- Malonie--- CH2CH2OC2H2CHz0CH2OH2OH 220.. Succinic. OHZCHzOOzHzCHgOCHzCHzOH 230.- Suberic- CHZOH2002HQCHZOCH2CH2OI'I 240.- Pimelic CHzOHzO OzHzCHzOCHzOHzOH: 250.. Nonedeeane diear- CHQOHzOCzHzOHzQCHzCHzOH oxy 10. 260.. Diglycolic CHZCHZOGZHZOHZOGHZGH2OH 270-- Methylene dibenzoic. CHzCHzO CzHzCHzO CHzOHzOH 280-- Stearyl malonic- CHzCHzO CzHzOH O CHZCHZOH 290-- Stearyl succinic.- CHzCHzOCaHzCHeOCHzCH-zOH 300.. Terephthalic OH2CH2OC:H2CH70CH2OH2OH TABLE IV RN N N N-R o Lnfio Ex. No HOOC-R-OOOH source R of ORO- Mnlrmin OHQCHZOH Siloninin CHzCHzOH Glutarir- CH2CH2OH Adinir- GHZOHZOH Suberic (CH3) OHZCH2OH Soham'n CHzCHzOH Pimelic CHzCHzOCHzOHzOH A Yelaio CHzOHgOH Nonodecane dicarboxylic CHgOHzOH Eicosane dicarboxylic- CHQOHZOH Diglyc CHzCHzOH Ethylene bisglycolic.. (CH3) CH2CH2OH Methylene carboxylic acid.--.- (CH3) CHzOHzOH Dilinoleic CHzCHzOH Stearyl malom'c. CH2CH2OH Lauryl succinic- CHzCHzOH Isotetradecyl succlm CHiCHzOH Phthnlin CHzCHzOCHzCHzOH Isophthalin CHzCHzOH Terephthalic. CHzCHzOH Glnraermin CH2CH OH THE ISOCYANATE REACTANT The isocyanate employed to react with the urethane precursor can vary widely. In general, they may be expressed as R(CNZ) where Z is oxygen or sulfur. This includes isocyanates and isothiocyanates and mixed isocyanates and isothiocyanates. 'For convenience this invention will be discussed largely in terms of isocyanates. In the above formula R is an aliphatic radical, a cycloaliphatic radical, an aromatic radical and the like, and x is a whole number equal to 1 or greater, for example 1 to 3.

However, we prefer to employ the diisocyanates in preparing derivatives used as anti-corrosion agents since they exhibit much greater activity than the monoisocyanates.

A preferred subgenus of this invention is that wherein the above partial structural formulae represents the polyisocyanate and more specifically the diisocyanates, which of course contain two distinct and separate isocyanate groups. Representative compounds of this subgenus are the polymethylene diisocyanates such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, etc.; the alkylene diisocyanates such as propylene-1,Z-diisocyanate, butylene-1,2-diisocyanate, butylene 1,3-diisocyanate, butylene- 2,3-diisocyanate; the alkylidine diisocyanates such as ethylidene diisocyanate, butylidene diisocyanate, and heptylidene diisocyanate. The cycloalkylene diisocyanates such as cyclopentylene-1,3diisocyanate, cyclohexylene-l,2-diisocyanate, cyclohexylene-l,4-diisocyanate; the aromatic diisocyanates such as m-phenylenediisocyanates, p-phenylene diisocyanate, 1-methylphenylene-2, 4-diisocyanate, l-methylphenylene-Z, 6-diisocyanate, 3,3'-bitolyl one-4, 4-diisocyanate, naphthylene-l, 4-diisocyanate, naphthylene-l,S-diisocyanate; aliphatic-aromatic diisocyanates, such as xylene-1,4-diisocyanate, xylene-1, 3-diisocyanate, 4,4-diphenylenemethane diisocyanate, 4,4'-diphenylenemethane diisocyanate, 4,4'-diphneylene-propane diisocyanate, etc.

The diisocyanates of the types listed in the above para graph are the ones which are most preferred for purposes of this invention. Examples of compounds containing more than two reactive groups of formula 'CNZ and of the preferred subgenus -N=&O which can be used, there may be mentioned 1,2,4-benzene triisocyanate and butane-1,2,2-triisocyanate.

Of course, it should be remembered that the polyisothiocyanates may be used instead of the polyisocyanates and representative examples would be those given above with the single change that the oxygen atom is substituted by sulfur.

Corresponding monoisocyanate derivatives of the above diisocyanates were also reacted, but, in general, they ex-' hibit far less activity in corrosion than the corresponding diisocyanates, for example, alkylisocyanate (e.g. methyl, ethyl, propyl, butyl, octadecyl, etc.); cycloalkyl (e.g. cyclopentylisocyanates, cyclohexylisocyanates) arylisocyanates (e.g. phenyl, naphthyl, etc.) alkaryl isocyanates (e.g. tolyl isocyanates, xylyl isocyanates), and the like.

The reactions involving isocyanates with urethane precursors are conducted in the same manner isocyanates have been reacted with other suitable reactants (see, for example, Chem. Rev. 43, 203-218 (1948), 57, 47-76 (1957).

THE URETHANE PRODUCTS The products of this invention are urethanes, for example,

where X comprises ll RO, (ROM etc.

wherein the hydroxy precursor and a monoisocyanate is reacted and H H N: NX--C -R' l in the case of the diisocyanate.

I Where the 'bicyclic amidines are used as hydroxy precursors, the following compounds are formed: s

'In general, the urethane is prepared by adding the isocyanate (a 50% solution, by weight,vin xylene) to the A hydroxy'cyclic amidine over a period of /2 hour to 1 l hour at 60-75 C. The addition is controlled so as to 5 maintain this temperature. The resulting product is then diluted with xylene so that it has 50% by weight of the R product. The following examples are illustrative. The 0 products formed are generally dark viscous liquids. ll

EXAMPLE IOaB To two moles of with the mono-isocyanates, and polymers are probably formed with diisocyanates, as may be expressed by the N N-C HaGHa O H following formula:

A 0 H IE! I N NX( /N- RN-OX- 011E in a well-stirred reaction vessel is added one mole of a 50% solution of toluene-2,4-diisocyanate in xylene over f a period of 30 minutes. The temperature during addi- O\ tion was 60-70 C. The product formed is N N- 0 0 I H H \A/ N NCHzCHaO-( i-N N-(J-OCHzCHz-N N Where the isocyanate is a isothiocyanate, the product (IJ CH (3 would be the analogous thiourethane, thus, 017E" 3 0171133 N X C IE FR EXAMPLE IOaD The process of the prior example is repeated except that p,p diphenylmethane diisocyanate is employed. R The product is O O Q N N-CHzCHrO-CN -CH NO0HcH,-N N 0 s 617113: 017E I EXAMPLE 10aC would be I 40 The process of the prior example is repeated except 7 that dianisidinediisocyanate, A S 01130 00113 N: NX NR i OCN NCO, R is employed.

' The product 0 OCH; 0([1Ha O i I] H H 11 i N NCHnCHzO-GN -N-COCH2CH2N N 0 uHaa Cn u and EXAMPLE IOaA A o 1] H H The process of the prior example 1s repeated except that NTX-CFN =R hexamethylene diisocyanate was employed. The prod- 0 net is I R 2 O O H H would be N N-OI-IzCHrCN(CHa)sN(iCHzCH-N N s a N N X g: g R I I T 017B Cn aa f v EXAMPLE 10216 R 2 and the others correspondingly changed to where the a The Process of the P example is repeated except that one mole of n 0 F i group is replaced with s N\/NCH:OH1OH .g. v p I $1711 13 and one mole of octadecyl isocyanate is employed to yield EXAMPLE lOaF The process of the prior example is repeated except that 2-naphthylisocyanate is employed. The product formed is N N-CH:CH2O( iN C li'iHas EXAMPLE 9bB The process of the prior example is repeated except that I C Has and ethyl isocyanate are employed to yield EXAMPLE 9bC The process of the prior example is repeated except that 2 moles of N N-CHzCHaOH I CnHss and 1 mole of m-toluene diisocyanate are employed to yield EXAMPLE 913A The process of the prior example is repeated except that hex-amethylene diisocyanate is employed to yield II E H II N N-CHzCHz-O-C-N-(CHfl)u-N-C-O-CHzCHi-N N I I 0 11 35 11 35 EXAMPLE 3.cA

The process of the prior example is repeated except that one mole of I I I HOOHzCHzN N N N-CHzCHzOH H2)e C and one mole of m-toluene diisocyanate are employed to yield a polymeric material, of the probable structure:

O I I I n H H n N N I I N-OHaOHaO-C-N NC-OOH2OH2- C-(CH2)5 C EXAMPLE 30B The process of the prior example is repeated except that one mole of I I I I V HOCHzCHz-N /N N N--CH2CH2OH o cHm-o and two moles of octadecyl isocyanate are employed to yield EXAMPLE 282113 The process of the prior example is repeated except that 2 moles of I C11 as and 1 mole of p,p diphenylmethane diisocyan'ate are employed to yield 15 EXAMPLE ZOaB The process of the prior example is repeated except that 2 moles of and 1 mole of 1,5 naphthalene diisocyanate are employed to yield TABLE V Preparation of Urethanes Hexamethylene diisocyanate Mixed isomers of toluene diisocyanate Dlanisidine diisocyanate 1,5-naphthalene diisocyanate Diphenylmethane, 4,4-diis0cyanate aA Hexamethylene diisocyanate 2,4-toluene diisocyanate Dianisidlne diisocyanate 10aD Diphenylmethane, 4,4-diisocyanate Ethyl isocyanate d-Naphthylisocyanate 10aG Octadecyl isocyanate IOaH 1,5 naphthalene diisocyanate Mixed isomers of 2,4-toluene dlisocyanate Hexamethylene diisocyanate 2,4-toluene diisocyanate ZOaA 1,5-naphthalene dilsocyanate 2821A Hexamethylene diisocyanate 28a b,b-Dlphenylmethane diisocyanate 2,4-toluene diisocyanate 28aD Dianisidine diisocyanate Hexamethylene diisocyanate Ethyl isocyanate 2,4-toluene diisocyanate Dianisidine diisocyanate Diphenylmethane, 4,4-diisoeyanate 2311A Hexamethylene diisocyanate 23bB 2,4-toluene diisocyanate 23bC Diphenylmethane 4,4-diisoeyanate 2,4-toluene dilsocyanate Octadeeyl isocyanate Dianisidlne diisocyanate Diphenylmethane 4,4-diisoeyanate 2,4-toluene dilsocyanate Dianisidine diisocyanate USE AS CORROSION INHIBITOR More specifically, this phase of the invention relates to the inhibition of corrosion in the petroleum industry with specific reference to producing wells, pipe lines, refineries, tank storage, etc.

The use of a corrosion inhibiting agent in the oil industry and other industries, and particularly for the protection of ferrous metals, is well known. For ex- 16 ample, see US. Patents Nos. 2,736,658, dated February 28, 1954, to Pfohl et al., and 2,756,211, dated July 24, 1956, to Jones, and 2,727,003, dated December 13, 1955, to Hughes.

More specifically then, and particularly from the standpoint of oil production, this aspect of the invention relates to inhibiting corrosion caused by hydrogen sulfide, carbon dioxide, inorganic acids, organic acids, combina tions of each with oxygen, and with each other and oxygen. More particularly, it relates to treating wells to mitigate metal corrosion and associated difiiculties.

It should also be pointed out that the corrosiveness of oil well brines will vary from Well to well, and the proportion of corrosion inhibiting agent added to the well fluids should also be varied from well to well. Thus, in some wells it may be possible to effectively control corrosion by the addition of as little as 5 ppm. of our new compositions to the Well fluids, Whereas in other wells, it may be necessary to add 200 ppm. or more.

In using our improved compositions for protecting oil well tubing, casing and other equipment which comes in contact with the corrosive oil-brine production, We find that excellent results are obtained by injecting an appropriate quantity of selected composition into a producing well so that it mingles with the oil-brine mixture and come into contact with the casing, tubing, pumps and other producing equipment. We, for example, introduce the inhibiting composition into the top of the casing, thus causing it to fiow down into the well and thence back through the tubing, etc. In general, we have found that this procedure suflices to inhibit corrosion throughout the entire system of production, and collection, even including field tankage.

In case serious emulsion or gel problems are encountered, demulsifiers are advantageously added. This is important not only to avoid the troublesome emulsions and gels themselves, but also to improve corrosion inhibition. The explanation of less efiective corrosion inhibition in the presence of emulsions apparently is that the inhibitor is somewhat surface-active. That is, it is concentrated at interfacial surfaces. Since this surface is great in an emulsion, most of the inhibitor will be concentrated in these interfaces and little will remain in the body of the oil for deposition on the metal surfaces. In many wells, oil-in-water type emulsions often occur naturally. In such wells the inhibitors herein described tending to form water-in-oil type emulsions, often decrease the emulsion problems naturally present. Thus, in addition to being effective corrosion inhibitors, the herein described products tend to eliminate emulsion problems which sometimes appear When some of the present day inhibitors are used in oil wells or refinery processing.

The method of carrying out our process is relatively simple in principle. The corrosion preventive reagent is dissolved in the liquid corrosive medium in small amounts and is thus kept in contact with the metal surface to be protected. Alternatively, the corrosion inhibitor may be applied first to the metal surface, either as is, or as a solution in some carrier liquid or paste. Continuous application, as in the corrosive solution, is the preferred method, however.

The present process finds particular utility in the protection of metal equipment of oil and gas wells, especially those containing or producing an acidic constituent such as H S, CO inorganic, organic acids, 0 and the like. For the protection of such wells, the reagent, either undiluted or dissolved in a suitable solvent, is fed down the annulus of the well between the casing and producing tubing where it becomes commingled with the fluid in the well and is pumped or flowed from the well with these fluids, thus contacting the inner Wall of the casing, the outer and inner wall of tubing, and the inner surface of all well-head fittings, connections and flow lines handling the corrosive fluid.

Where the inhibitor composition is a liquid, it is conveniently fed into the well annulus by means of a motor driven chemical injector pump, or it may be dumped periodically (e.g., once every day or two) intothe annulus by means of a so-called boll weevil device or similar arrangement. Where the inhibitor is a solid, it is dropped into the well as a solid lump or stick, blown in as a powder with gas, or it may bewashed in with a small stream of. the Well fluids or other liquid. Where there is gas pressure on the casing, it is necessary, of course,- to employ any of these treating methods through a pressure equalizing chamber equipped to allow introduction of reagent into the chamber, equalization of pressure between chamber and casing, and travel of reagent from chamber to well casing. V I

Occasionally, oil and gas wells are completed in such a manner that there is no opening between the annulus and the bottom of the tubing or pump. This results, for example, when the tubing is surrounded at some point by a packing held by the casing or earth formation below the casing. In such wells the. reagent may be introduced into the tubing through a'pressure equalizing vessel, after stopping the flow of fluids. After being so treated, the well should be left closed in for a period of time suflicient to permit the reagent to drop to the bottom of the well.

For injection into the well annulus, the corrosion inhibitor is usually employed. as. a solution in a suitable solvent, such as mineral oil, methylethyl ketone, xylene, kerosene, or even water. The selection of solvent will depend much upon the exact reagent being used and its solubility characteristics. -It is also generally desirable to employ a solvent which will yield. a solution of low freezing point, so as to obviate the necessity of heating the solution and injection equipment during winter use.

For treating wells with packed-elf tubing, the use of solid sticks or plugs of inhibitor is especially convenient. These are prepared by blending the inhibitor with a mineral wax, asphalt or resin in a proportion sufiicient to give a moderately hard and high-melting solid which canbe handled and fed into the well conveniently.

The amount of corrosion preventive agent required in our process varies with the corrosiveness of the system, but where a continuous or semi-continuous treating pro cedure is carried out as described above, the addition of reagentin the proportion of from parts per million to 1000 parts per million or more parts of corrosive fluid will generally provide protection.

These corrosion inhibitors can be used in combination with other well-known corrosion inhibitors, for example, the cyclic amidine structures, the amido cyclic amidine structures, andthe amino cyclic amidine structures, as disclosed in the Blair and Gross Reissue Patent .No. 23,227. When the herein described products are mixed with corrosion inhibitors of the conventional type in the ratio of one-to-three, one-to-one, three-to-one, or the like, in numerous instances the effectiveness of the corrosion inhibitor thus obtained is often significantly greater than the use of either one alone.

Since these products are basic they can be combined with various acids to produce salts in which oil solubility is increased or decreased. Likewise, water solubility is increased or decreased. For instance, the products are mixed with one or more moles of an acid, such as higher fatty' acids, dimerized fatty acids, naphthenic acids, acids obtained by the oxidation of hydrocarbons, as.well as sulfonic acids such as dodecylbenzene sulfonic'acid, petroleum mahogany acids, petroleumgreen acids, etc. I

What has been said in regard to the acids which increase oil solubility and'decrease water solubility applies with equal 'force and effect to acids of the type, such as acetic acid, hydroxyacetic acid, gluconic acid, etc., all of which obviously introduce hydrophile character when they form salts or complexes, if complexes are formed. For example, any of the acids described above in preparing the cyclic amidines are useful in preparing these salts.

As pointed out previously, the addition of corrosion inhibitors, particularly in the form of a solution by means of a metering pump or the like, is common practice. The particular corrosioninhibitors herein described are applied in the same manner as other corrosion inhibitors intended for use for thesame purpose. For sake of brevity, as to the use of the corrosion inhibitor and its solution in a suitable solvent such as mineral oil, methyl ethyl ketone, xylene, kerosene, high boiling aromatic solvent, or. even water.

The following examples are presented to illustrate the superiority of the instant compounds as corrosion inhibitors.

Static weight loss tests.--These testshave been run on bothv synthetic and naturally occurring fluids. The test procedure involved the measurement of the. corrosive action ofthe fluids. inhibited by the compositions herein described upon sandblasted S.A.E. 1020 steel coupons measuring A; x 3% inches under conditions approximating those found in an actual producing well, and the comparison thereof with results obtained by subjecting identical test coupons to the corrosive action of identical fluids containing no inhibitor.

Clean pint bottles werecharged with 200 ml. of 10% sodium chloride solution saturated with hydrogen sulfate and 200 ml of mineral spirits and a predetermined amount of inhibitor was then added. In all cases the inhibitor concentration wasbased on thetotal volume of fluid. Weighed couponswere then added, the bottles tightly sealed and allowed to remain at room temperature for 3 days. The coupons were then removed, cleaned by immersion in inhibited 10% hydrochloric acid, dried and weighed. 1

The changes in the weight of thecoupons during the corrosion test were taken as a measurement of theeifectiveness of the inhibitor compositions. Protection percentage was calculated for each test coupon taken from the inhibited fluids in accordance with the following formula:

X =percent protection in which L istheloss in weight of the coupons taken.

TABLE VI Static Weight Loss Tests at 100 P.P.M. Based on Total Fluids N NOH2CH2OH Inhibitor Mg. loss Percent Ex. (avg; 3 protec- Remarks values) tion R Diisocyauate Blank 171. 5 i The fluids in IOaD C17Ha3 4,4-dipheny1- 32. 6 80. 9 all examples methane. were not 10a (lnHaa Hexamethylene 36. 4 78. 8 fully satulOaB 017E355 l t-toluene" 24.1 85.9 rated with 10210 0111133 Dianisidine- 37. 9 77. 8 H 8 pH 6 65 10aI 0 1133 Mixed isomers 25. 7 84. 9 The fluids of 2,4-t0luene. were 10% 102113 0171133 d0 52. 4 79.6 sodium chlorlHau None 1 124. 6 27. 3 ride and mineral spirits.

1 Free alcohol.

Stirring tests-These tests are runon synthetic fluids. The procedure involves the comparison of the amount of iron in solution after a predetermined interval of time of contact of a standardized iron surface with a twophase corrosive medium with similar determinations in systems containing'inhibitorsI Six hundred ml. beakers equipped with stirrers and heaters are charged with 400 ml. of 10% sodium chloride spirits. The liquids are brought to temperature and a 1 x 1 inch sand blasted coupon is suspended by means of a glass hook approximately midway into the liquid phase of the beaker. The stirrer is adjusted to agitate the liquids at such a rate as to provide good mixing of the two layers.

After 30 minutes samples of the aqueous phase are taken and the iron content of each sample is determined by measuring the color formed by the addition of hydrochloric acid and potassium thiocyanate in a photoelectric colorimeter.

The protection aiforded by an inhibitor is measured by comparison of the amount of light absorbed by inhibited and uninhibited samples run simultaneously. .Percent protection can be determined by the following formula:

where A is the present light absorbed by an uninhibited sample and A is the same value for an inhibited sample.

TABLE VII Stirring Tests at Room Temperature-All Inhibitors Were Used at 40 P.P.M. Based on Total Fluid 100=pereent protection Percent absorption sample 2) Percent absorption b ank Inhibitor Percent protection Commercial A inhibito Commercial B inhibitor--- N N-CHCHOH 2s 22 TABLE VIII Stirring Tests at 140 FA 40 P.P.M. Based on Total Fluids Inhibitor Percent absorp- Percent absorption tion (blank sample Percent protection R Diisocyanate IOaB IOaA aH 10aL IOaC laB 2,4-toluene 58 Hexamethylene. 58 1,5-naphthalene.. 58 Mixed isomers 58 2,4-to1uene. Diphenyl- 58 methane. Dianisidine 60 Mixed isomer of 60 2,4-toluene.

\IKI qcooom Commercial A ibitor. Commercial B" ibitor. Commercial 1 or. Commercial 59 19 D ibitor. nHzs None I 59 53 10. 2

1 It has been noted that some compounds have a definite actuation energy so these tests are usually run at room temperatures as Well as at elevated temperatures.

{Free alcohol.

' Engineers, New York, November 1952).

20 TANKER TESTS (CYCLE TEST) This test wasdescribed by Malcolmson et al. (Annual Meeting of the Society of Naval Architects and Marine It involves the measurement by weight loss of coupons which have been subjected to the corrosive action of sea water and a hydrocarbon for a week followed by contact for one Week with sea water and air, and the comparison there to the weight loss of coupons subjected to a similar test in which a small amount of inhibitor has been added to the hydro carbon phase.

In using the improved compositions for the protection of oil well casing, tubing, and other equipment which comes in contact with the corrosive oil and brine, excellent results have been obtained by injecting an appropriate quantity of the selected composition into a producing well so that it mingles with the oil brine mixture and comes in contact with the casing, tubing, pumps and other producing equipment. For example, the inhibiting composition may be introduced into the top of the casing, thus causing it to flow down into the well and back through the tubing. This system sufiices to inhibit corrosion in the entire system.

Using this system compound 10aB was used in four producing wells in Kansas. To evaluate the protection afforded by this chemical, small, mild steel plates which had been sand-blasted and weighed were exposed to the Well fluids by insertion into the flow line near the well head for periods of two weeks. The specimens were retained on a plug by means of a plastic which afiorded insulation for the plates so as to prevent interferences by galvonic currents. After exposure the coupons were cleaned by a brief contact with inhibited hydrochloric acid, dried and weighed.

The results were expressed in mils penetration per year which expresses the depth of surface, in thousandths of an inch, removed in a year assuming the corrosion had occurred uniformly over the entire surface. This value was. readily calculated by the simple formula Weight of metal removed In pumping wells it has been found that when penetrations are lowered to a value of 1 MPY or less, generally acceptable protection can be expected. Tolerable rates may range up to 4 MPY. Obviously the lower values. are more acceptable.

Experience has shown good correlation between penetration rates as shown by coupons and the Well corrosion history.

The effectiveness of the described compositions in inhibiting corrosion occurring in oil wells can be better and more fully understood by reference to the results obtained in the aforementioned well tests. In these tests a six week control period was first set aside during which time three 21 sets of coupons were used in each well with the exposure time of each set being approximately two weeks, after which interval the MPY values were determined as previously described. During this control period a well- 22 water spotting in lacquers, anti-skinning, pigment flushing, grinding and dispersing, anti-feathering in inks.

Petroleum: germicide in flood water treatment, deernulsifyirig fuel oil additives, anti-strip agent in asphalt known commercial corrosion inhibitor previously deteremulsions and cutbacks. mined to be the best for the well was used in the wells Textiles: in rubberizing, textile oils, dyeing assistants, at a rate of approximately two gallons per week per well softening agents. with treatment being semi-Weekly at approximately n M1scellaneous: bentonite-armne complexes, metalgallon per treatment per well. At the end of this control amine compleXsz Preparation of p l p period the new composition 100B was injected using the q rn Plastlsols, and E repellentssame treating procedure and rate as during the previo Having thus described our lnvention, what we claim as control period. The results of these tests are described e and d i e Obtain y Letters Pa t is in the following table: 1. A method of inhibiting the corrosion of ferrous Control period With 1021B Well name and number M /8-M/22 M/22-M/l5 M/5-M/l9 Avg. M/3M/l6 M/lG-M/3O M/1-M/15 Avg.

Koogler #86 8.30 .07 14. 33 10. 90 10.07 0. 4'4 1.72 4. 0s Koogler #92-.- e. 84 1. 52 5. 90 4. 79 1.15 1. 03 1. 33 1.17 Hull-Higgins #1 3. 69. 1. 05 1. 21 1.98 0. s7 0. 4s 1. 57 0. 97 Bender D #4 s. 42 6. e5 4. 25 6. 44 2. 71 5. 53 3. 05 3.76

1 M indicates a month without specific designation.

The unexpected superiority of the instant compounds metalsin hydrocarbon systems which is characterized by over the untreated hydroxyoliphatic amidines and other contacting such metals with a compound of the formula: of the best commercially available inhibitors has clearly N N been demonstrated. I (OBDH (CBDH OTHER USES N N 7 These products are effective not only as corrosion inl l (ADM-5 (AO)1-5 h1b1tors but can be used for a number of other purposes. For instance, they can be used as asphalt additives to ini (3:0 crease the adhesiveness of the asphalt to the mineral ag- NH NH gregates. In the form of water soluble salts, they are gg z g gfg tg f g t g z fgg g 2g :2: where B is selected from the group consisting of hydrotensiv y x elk l ation b means of e t h lene o xide r0 1- gen and a'lower alkylrgmup A is a lower alkylene group y y Y y p R having at least two carbon atoms, R is a hydrocarbon ene oxide, butylene oxide, or the like pnor to react1on 40 with the isocyanate. These are oxyalkylated and still have oil solubility as, for example, by the addition of propylene oxide or butylene oxide, or are oxyalkylated to produce water solubility such as, for example, by means of ethylene oxide or glycide. They are. also oxyalkylated by combinations of propylene oxide and ethylene oxide so that both water solubility and oil solubility remain. Thereupon they are reacted with isocyanates. Such products are useful for a variety of purposes and particularly for those where nonionic surfactant or sequestered cationic surfactants are indicated.

In addition, the compounds of this invention have the following application:

Agriculture: Additive for kerosene, phenothiazine, pyrethrum sprays, fungicides, herbicidal oils.

Anti-static treatment: for hotel rugs, hospital floors, automobile upholstery, plastic and wax polishes, wool oils, lubricants for synthetic fibers.

Building materials: water repellent treatment for plaster, concrete, cement, roofing materials, =air entrainment, floor sealers, linoleum.

Cosmetics: formulation of anti-perspirants, deodorants, sun screens, hair preparations.

De-emulsifying': in antibiotic extraction, breaking crude oil and water-gas for emulsions.

Detergents: metal cleaning; emulsions, lens cleaners, floor oil's, dry cleaning detergents, radiator flushes,-cesspool acid, boiler scale solvents, germicidal corrosion-in hibited acid detergents for dairies, enamel equipment, toilet bowls.

Leather: flat liquoring oils, pickling, acid degreasing, dye fixative.

Metals: rust preventive oils, cutting oils, water displacing compounds, pickling inhibitor, solvent degreasing.

Paints: for improved adhesion of primers, preventing having 1- 36 carbon atoms, and R is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms, R beingin both instances the same.

2. A- method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula lHm-z (h 2)2-s [a l. [a l.

1 :0 NH l TH it it where-Risa hydrocarbon having1-36 carbon atoms and 23 R is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms, R being in both instances the same.

4. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula where B is selected from the group consisting of hydrogen and a lower alkyl group, A is a lower alkylene group having at least two carbon atoms, R is a hydrocarbon having 1-36 carbon atoms, R is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms.

5. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula where R is a hydrocarbon having 1-36 carbon atoms and R is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms.

7. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound prepared by reacting with a diisocyanate of the formula ONORCNO where B is a member selected from the group consisting of hydrogen and a lower alkyl group, A is a lower alkylene group having at least two carbon atoms, R is a hydrocarbon having 1-36 carbon atoms and R is a hydrocarbon having 1-30 carbon atoms.

8. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound prepared by reacting Hr) 2-3 (CH2) 2-3 l 1: I 1-5 H H with an isocyanate of the formula ONCRCNO where R is a hydrocarbon having 136 carbon atoms and R is a hydrocarbon having 1-30 carbon atoms.

9. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound prepared by reacting with a diisocyanate of the formula ONCR'CNO where R is a hydrocarbon having l36 carbon atoms and R is a hydrocarbon having l-3O carbon atoms.

10. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula where R is a hydrocarbon having 1-36 carbon atoms, and R' is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms.

11. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula where R is a hydrocarbon having 136 carbon atoms and R is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms.

12. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula where R is a hydrocarbon having 1-36 carbon atoms and R is a hydrocarbon moiety of a hydrocarbon isocyanate having 1-30 carbon atoms.

13. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems which is characterized by contacting such metals with a compound of the formula where R is a hydrocarbon having 1-36 carbon atoms and R' is a hydrocarbon moiety hydrocarbon isocyanate having 1-30 carbon atoms.

14. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with 25 15. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with 16. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with l C n aa 17. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with I OH: 171 2 18. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with 19. A method of inhibiting the corrosion of ferrous 26 metals in hydrocarbon systems characterized by treating such metals wih 20. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with Alias 2 21. A method of inhibiting the corrosion of ferrous metals in hydrocarbon systems characterized by treating such metals with such metals with References Cited in the file of this patent UNITED STATES PATENTS 2,468,163 Blair et a1 Apr. 26, 1949 2,792,390 Stromberg May 14, 1957 2,794,810 Cusic June 4, 1957 2,987,515 Stromberg et al June 6, 1961 

1. A METHOD OF INHIBITING THE CORROSION OF FERROUS METALS IN HYDROCARBON SYSTEMS WHICH IS CHARACTERIZED BY CONTACTING SUCH METALS WITH A COMPOUND OF THE FORMULA: 